Éditeur(s) : HAL CCSD European Geosciences Union (EGU)
Résumé : International audience
The transformation of nonlinear long internal waves in a two-layer fluid is studied in the Boussinesq and rigid-lid approximation. Explicit analytic formulation of the evolution equation in terms of the Riemann invariants allows us to obtain analytical results characterizing strongly nonlinear wave steepening, including the spectral evolution. Effects manifesting the action of high nonlinear corrections of the model are highlighted. It is shown, in particular, that the breaking points on the wave profile may shift from the zero-crossing level. The wave steepening happens in a different way if the density jump is placed near the middle of the water bulk: then the wave deformation is almost symmetrical and two phases appear where the wave breaks.
ISSN: 1023-5809

hal-00331099
https://hal.archives-ouvertes.fr/hal-00331099
https://hal.archives-ouvertes.fr/hal-00331099/document
https://hal.archives-ouvertes.fr/hal-00331099/file/npg-14-247-2007.pdf

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Variation of dead wood decay rates among tropical trees remains one source of uncertainty in global models of the carbon cycle. Taking advantage of a broad forest plot network surveyed for tree mortality over a 23-year period, we measured the remaining fraction of boles from 367 dead trees from 26 neotropical species widely varying in wood density (0.23–1.24 g cm-3) and tree circumference at death time (31.5–272.0 cm). We modeled decay rates within a Bayesian framework assuming a first order differential equation to model the decomposition process and tested for the effects of forest management (selective logging vs. unexploited), of mode of death (standing vs. downed) and of topographical levels (bottomlands vs. hillsides vs. hilltops) on wood decay rates. The general decay model predicts the observed remaining fraction of dead wood (R2 = 60%) with only two biological predictors: tree circumference at death time and wood specific density. Neither selective logging nor local topography had a differential effect on wood decay rates. Including the mode of death into the model revealed thatstanding dead trees decomposed faster than downed dead trees, but the gain of model accuracy remains rather marginal. Overall, these results suggest that the release of carbon from tropical dead trees to the atmosphere can be simply estimated using tree circumference at death time and wood density.
ISSN: 0029-8549

hal-01094187
https://hal-agroparistech.archives-ouvertes.fr/hal-01094187
DOI : 10.1007/s00442-010-1602-8

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Children are exposed to toxic metals and metalloids via their diet and environment. Our objective was to assess the aggregate chronic exposure of children aged 3–6 years, living in France, to As, Cd, Cr, Cu, Mn, Pb, Sb, Sr, and V present in diet, tap water, air, soil and floor dust in the years 2007–2009. Dietary data came from the French Total Diet Study, while concentrations in residential tap water, soil and indoor floor dust came from the ‘Plomb-Habitat’ nationwide representative survey on children's lead exposure at home. Indoor air concentrations were assumed to be equal to outdoor air concentrations, which were retrieved from regulatory measurements networks. Human exposure factors were retrieved from literature. Data were combined with Monte Carlo simulations. Median exposures were 1.7, 0.3, 10.2, 34.1, 60.3, 0.7, 0.1, 44.3, 1.5 and 95th percentiles were 4.4, 0.5, 15.8, 61.3, 98.3, 2.5, 0.1, 111.1, 2.9 μg/kg bw/d for As, Cd, Cr, Cu, Mn, Pb, Sb, Sr, and V respectively. Dietary exposures dominate aggregate exposures, with the notable exception of Pb - for which soils and indoor floor dust ingestion contribute most at the 95th percentile. The strengths of this study are that it aggregates exposures that are often estimated separately, and uses a large amount of representative data. This assessment is limited to main diet and residential exposure, and does not take into account the relative bioavailability of compounds. These results could be used to help target prevention strategies.
ISSN: 0160-4120

inserm-01404061
http://www.hal.inserm.fr/inserm-01404061
http://www.hal.inserm.fr/inserm-01404061/document
http://www.hal.inserm.fr/inserm-01404061/file/rev1%20-%20MS%20Expo%20metals.pdf
DOI : 10.1016/j.envint.2016.10.009

Éditeur(s) : XIIèmes Journées Nationales Génie Côtier - Génie Civil. Cherbourg, 12-14 juin 2012. n°12. Levacher D, Sanchez M, et Guillou S (Eds). ISBN 978-2-35921-008-8. Thème 5 : Energies marines. pp.809-818
Résumé : Les fortes vitesses rencontrées à l’entrée de la Baie du Mont Saint-Michel font de cet environnement macro-tidal un endroit privilégié, en termes de ressources énergétiques, pour l’implantation d’une ferme d’hydroliennes. Afin d’établir plus précisément son potentiel énergétique et d’évaluer l’impact de l’implantation de telles machines sur son hydrodynamisme, une modélisation hydrodynamique de la Baie du Mont Saint-Michel est mise en oeuvre à l’aide du modèle de circulation régionale MARS3D (LAZURE & DUMAS, 2008) dans sa version tridimensionnelle. La validation hydrodynamique de cette configuration est réalisée à partir de comparaisons à des mesures courantologiques récentes (KERVELLA, 2010). A partir de cette modélisation, une cartographie du potentiel énergétique de la Baie est établie et les endroits propices à l’installation de structures récupératrices de l’énergie des courants sont identifiés. L’impact de l’implantation d’une ou plusieurs structures à l’un de ces endroits sur l’hydrodynamique de la Baie est évalué : l’effet de l’extraction d’énergie des courants est modélisé par l’implémentation d’un nouveau terme puits, correspondant à une force de retard colinéaire à l’écoulement (DEFNE et al., 2011), dans les équations du mouvement de MARS3D. Les résultats présentés pour 2 valeurs d’extraction de l’énergie disponible (25% et 55%) montrent que l’impact d’un parc de petite superficie sur les courants reste très local.

Droits : Editions Paralia CFL
http://archimer.ifremer.fr/doc/00195/30599/29055.pdf
DOI:10.5150/jngcgc.2012.088-B
http://archimer.ifremer.fr/doc/00195/30599/

Éditeur(s) : HAL CCSD European Geosciences Union
Résumé : We propose to assess the error done when temperature is considered as a conservative tracer in fluviokarst studies. As a matter of fact, heat exchanges occur between karstic Conduit System (CS) and Porous Fractured Matrix (PFM) that prevents from using this approximation without caution. The conservative tracer approximation boils down to consider the cooling of CS water by PFM flow in an open thermodynamic system where the CS is bounded by an Adiabatic Wall (AW). The resulting CS water temperature contrasts with the one obtained from more complete models (CW), which also take into account heat conduction within the CS, within the PFM, and from the CS to PFM through CS a Conductive Wall. In order to assess first orders of this error, the dimensionless equations, characteristic of CS cooling by PFM, have been solved thanks to Alternate Finite Difference Implicit methods both in AW and CW configurations. Four groups of dimensionless numbers appear in the various terms of energy and mass equations among which the Peclet and Reynolds numbers depict the large morphologic and hydrologic variability of natural karstic systems. A parametric exploration of the differences between AW and CW models has then been conducted vs. Peclet numbers (Pe numbers varying from 106 to 109, at constant CS Reynolds number) and vs. Reynolds numbers (Red varying from 103 to 107, at constant Peclet number). The error curves bound finite volumes in the Peclet–Reynolds space that converge uniformly to zero for the extreme values of these parameters. However, for Peclet and Reynolds numbers characteristic of realistic fluviokarst configurations, the errors reach finite values, that give first order information assessing the error done by considering temperatures as conservative tracers. Maximum relative errors around 10−2 (in fact 0.0092) have been found varying Pe; while it remained slightly lower than 0.7 × 10−2 varying Red. An illustrative example of the temperature conservative tracer AW approximation is presented with the data obtained from the main morphologic and hydrologic properties of the Cent–Font resurgence (Hérault, France). According to the results, the error reached at the output of the fluviokarst is 0.00613 (for Pe = 1.4993 × 108 and Red = 4.2969 × 104). When rescaled to the physical domain, this error leads to a temperature difference of 1.77 K between the CW and AW configurations.
ISSN: 1812-2108

hal-01358348
https://hal.archives-ouvertes.fr/hal-01358348
https://hal.archives-ouvertes.fr/hal-01358348/document
https://hal.archives-ouvertes.fr/hal-01358348/file/hessd-11-169-2014.pdf
DOI : 10.5194/hessd-11-169-2014

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We investigated the response of the crystal structure, lattice parameters, and unit-cell volume of hydrous layered silicate phlogopite at conditions relevant to subduction zone settings. We have used first principles simulation based on density functional theory to calculate the equation of state and full elastic constant tensor. Based on the generalized gradient approximation, the full single crystal elastic constant tensor with monoclinic symmetry shows significant anisotropy with the compressional elastic constants: c11 = 181 GPa, c22 = 185 GPa, c33 = 62 GPa, the shear elastic constants c44 = 14 GPa, c55 = 20 GPa, c66 = 68 Ga, and c46 = −6 GPa; the off diagonal elastic constants c12 = 48 GPa, c13 = 12 GPa, c23 = 12 GPa, c15 = −16 GPa, c25 = −5 GPa and c35 = −1 GPa at zero pressure. The elastic anisotropy of phlogopite is larger than most of the layered hydrous phases relevant in the subduction zone conditions. The shear anisotropy, AVS for phlogopite is ∼77% at zero pressure condition and although it decreases upon compression it remains relatively high compared to other hydrous phases relevant in the subduction zone settings. We also note that the shear elastic constants for phlogopite are relatively low. Phlogopite also has a high isotropic bulk VP/VS ratio ∼2.0. However, the VP/VS ratio also exhibits significant anisotropy with values as low as 1.49. Thus, phlogopite bearing metasomatized mantle could readily explain unusual VP/VS ratio as observed from seismological studies from the mantle wedge regions of the subduction zone.
ISSN: 0031-9201

hal-01115670
https://hal.archives-ouvertes.fr/hal-01115670
DOI : 10.1016/j.pepi.2014.05.004

Résumé : Schemes optimisation for genetic improvement for growth of Penaeus stylirostris requires the development of technologies for grading shrimps easily. This work shows that bar and mesh graders are very suitable for early selection at post-larval stages, as long as early growth is heritable. Experimental data sets lead to the equations which give the grading weight as a function of the dimensions of the graders. Mesh graders which allow an earlier selection than bar graders (PL19 instead of PL25) open a new way to implement experimental selection into production hatcheries.
L’optimisation des schémas d’amélioration génétique de la croissance de Penaeus stylirostris, passe nécessairement par la mise au point des techniques de tri rapide et facile à mettre en oeuvre par les acteurs de la filière. Ce travail montre que les trieurs à barreaux ou à maille sont des outils adaptés à une sélection précoce en sortie d’écloserie, dans la mesure où la croissance précoce s’avèrerait héritable. Les tris expérimentaux ont permis d’établir les formules permettant de calculer les poids de tris en fonction des dimensions des trieurs. Les trieurs à maille qui permettent de trier les crevettes dès PL19 ouvrent des perspectives intéressantes pour intégrer une démarche de sélection expérimentale au sein des écloseries de production.

Droits : 2000 Ifremer
http://archimer.ifremer.fr/doc/00203/31439/29836.pdf
http://archimer.ifremer.fr/doc/00203/31439/

Éditeur(s) : HAL CCSD
Résumé : 18 pages
This article adresses questions on localization and microlocalization in the framework of the so called (C,E,P)-algebras of generalized functions. We give new results on nonlinear properties of the asymptotic singular spectrum in the multi-parameter case, a tool to describe the singularities of generalized solutions associated to problems which are classically ill-posed. Wa apply the theory to a transport equation with strongly irregular coefficients and initial data.
https://hal.univ-antilles.fr/hal-00761112

hal-00761112
https://hal.univ-antilles.fr/hal-00761112
https://hal.univ-antilles.fr/hal-00761112/document
https://hal.univ-antilles.fr/hal-00761112/file/DT2010-03_Devoue_al3.pdf

Éditeur(s) : HAL CCSD
Résumé : International audience
This paper is concerned with a null controllability problem for nonlinear parabolic equations appearing in mathematical biology. We consider a system of two equations with a nonlocal nonlinearity, in a bounded domain Ω of ℝN0, N0 being a positive integer sufficiently small. Such models can be used in the context of dynamics of biological systems to describe the migration of population (of bacteria in a container). Our aim is to find a control common to both equations, which solves the null controllabillity of the studied system under constraints on the state. A similar control problem has recently been addressed for the Laplace operator, so the present paper extends those results.
2017 Proceedings of the Conference on Control and its Applications
Pittsburgh, United States

Droits : http://hal.archives-ouvertes.fr/licences/copyright/
hal-01567339
https://hal.archives-ouvertes.fr/hal-01567339
DOI : 10.1137/1.9781611975024.3

Éditeur(s) : Gauthier-Villars
Résumé : The wind, temperature and current data collected during the joined French-USA FOCAL/SEQUAL programme carried in the equatorial Atlantic band in 1983 and 1984, allowed for the first time a simultaneous study of both the equatorial and coastal (5-degrees-N) upwellings along 4-degrees-W. At the equator, the decreases of both the surface temperature and the depth of the thermocline in boreal summer are correlated with the zonal component of the local windstress in the period band 1-2 months. This corresponds to the time required by the thermocline to lift up at 0-4-degrees-W in the presence of an easterly wind. The local wind cannot however explain the entire vertical variability of the thermal structure at 0-4-degrees-W. The correlation function shows in addition that the temperature there is highly correlated to the wind recorded at St Peter and St Paul Rocks (SPP) in the period band 0-2 months. This time scale is the one required by the Kelvin and Rossby waves to propagate along the equator through equatorial wave guide dynamics. The influence of these waves seems particularly important when considering the upward displacements of the thermocline both in February-March when the winds abruptly relax and in November-December when the wind at 0-4-degrees-W is southwesterly with no secondary negative maximum in the wind record at 1-degrees-N-29-degrees-W (SPP), contrary to the climatological wind field. The computation of the different terms of the heat equation applied to an homogeneous surface layer shows that the cooling is entirely due to vertical advection and eddy diffusion. The cooling would be more effective without the atmospheric heat flux and the horizontal advection of heat transported both by the South Equatorial Current at the surface and the southward current at the bottom of the mixed layer. At the coast, the amplitude and duration of the upwellings are not constant all along the coast: in boreal summer, they are maximum east of the two capes (Palmas and Three Pointes) while in winter the strength of the cooling is maximum in the east of Cape Palmas and then decreases eastward. The meridional slope of the thermocline off the coast concerns a distance which is much larger than the internal Rossby radius of deformation and is coherent with the latitudinal extension and intensity of the Guinea current both in summer and winter. In addition to this geostrophic adjustment, the upward tilt of the thermocline in summer is enhanced by the intensification of the component of the wind parallel to the coast. The application of a simple linear model forced with an eastward wind at that time explains the surface maximum cooling at the coast and the current distribution in both vertical and meridional directions. The two maxima of the zonal component of the Guinea current, in summer (main one) and in winter are in phase with the intensity of the vertical component of the windcurl. The application of the Sverdrup equations shows that the current speeds computed, for both seasons, are of the same order of magnitude as the speeds observed.
Oceanologica Acta (0399-1784) (Gauthier-Villars), 1991 , Vol. 14 , N. 3 , P. 223-240

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00101/21252/18865.pdf
http://archimer.ifremer.fr/doc/00101/21252/

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
1. Estimating forest above-ground biomass (AGB), or carbon (AGC), in tropical forests has become a majorconcern for scientists and stakeholders. However, AGB assessment procedures are not fully standardized andeven more importantly the uncertainty associated with AGB estimates is seldom assessed.2. Here, we present an R package designed to compute both AGB/AGC estimate and its associated uncertaintyfrom forest plot datasets, using a Bayesian inference procedure. The package builds upon previous work onpantropical and regional biomass allometric equations and published datasets by default but it can alsointegrate unpublished or complementary datasets in many steps.3. BIOMASS performs a number of standard tasks on input forest tree inventories: i) tree speciesidentification, if available, is automatically corrected; ii) wood density is estimated from tree species identity;iii) if height data are available, a local height-diameter allometry may be built; else height is inferred frompantropical or regional models; iv) finally, AGB/AGC are estimated by propagating the errors associated withall the calculation steps up to the final estimate. R code is given in the paper and in the appendix forillustration purpose.4. The BIOMASS package should contribute to improved standards for AGB calculation for tropical foreststands, and will encourage users to report the uncertainties associated with stand-level AGB/AGC estimatesin future studies.
ISSN: 2041-210X

hal-01558180
https://hal.archives-ouvertes.fr/hal-01558180
DOI : 10.1111/2041-210X.12753

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : En este trabajo se pretende hacer una aproximación a las posibilidades que tiene el espacio público de las ciudades costeras y de las islas como elemento de integración social. Para ello veremos que el diseño de estos espacios desde el punto de vista de la diversidad humana es muy importante, ya que si a la hora de diseñar tenemos en cuenta todas las posibilidades, podremos generar espacios que ayuden a las personas a sociabilizarse. En las zonas costeras contamos con cuestiones específicas y en el caso concreto de las islas y playas en el que existe espacio limitado, es importante definir este rol del espacio público.La humanización del espacio público va de la mano de la accesibilidad, es por este motivo que aplicar criterios de Diseño para Todos y Accesibilidad Universal en el diseño del espacio público nos permite la democratización del mismo, de tal modo que puede ser disfrutado por todos los ciudadanos en igualdad de condiciones. En las islas y las zonas costeras, la exclusión social de grupos poblacionales por falta de accesibilidad puede resultar preocupante ya que la limitación física del espacio reduce mucho las posibilidades de crecimiento de las personas.
Cette étude propose une approche sur les possibilités de faire de l’espace public des villes côtières et des îles un élément d’intégration sociale. Pour cela il est important que la conceptualisation de ces espaces intègre les dimensions de la diversité humaine. Si lors de la conception toutes les possibilités sont prises en compte, il est possible de construire des espaces qui participent à la sociabilisation des personnes. Dans les zones côtières se posent des questions spécifiques et concrètes autour de l’accessibilité aux plages et aux îles dans lesquelles l’espace est limité. Il est important de définir le rôle de l’espace public.L’humanisation de l’espace public va de pair avec la question de l’accessibilité, d’où l’importance d’intégrer les dimensions de l’accessibilité pour tous dans l’aménagement de ces espaces. C’est une question de démocratie, tous les citoyens doivent pouvoir en profiter quelle que soit leur condition. Dans les espaces côtiers, l’exclusion sociale de certaines catégories de populations en raison du manque d’accessibilité est d’autant plus préoccupante que le milieu physique est plus contraignant.
This paper intends to approximate the possibilities that the public space of coastal cities and islands have as an element of social integration. For this we will see that the design of these spaces from the point of view of diversity is very important, since when designing we take into account all the possibilities of generating spaces that help people to become socialized. In coastal areas we have specific things and in the specific case of islands and beaches where there is limited space, it is important to define this role of public space.The humanization of public space goes hand in hand with accessibility, it is for this reason that it applies criteria of Design for All and Universal Accessibility in the design of the public space allows us the democratization of it, in such a way that can be enjoyed by all Citizens in equal conditions In the islands and coastal areas, social exclusion of population groups due to lack of accessibility can be of concern and that physical limitation of space reduces the chances of growth of people.

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.10752
http://journals.openedition.org/etudescaribeennes/10752

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Lead in homes is a well-known source of childhood lead exposure,which is still of concern due to the health effects of low lead doses. This study aims to describe lead contamination in the homes of children aged 6 months to 6 years in France (without overseas). Between October 2008 and August 2009 ,484 housing units were investigated. Lead in tap water and total and leachable lead levels from floor dust, outdoor soils and paint chips were measured. X-ray fluorescence measurements were carried out on non-metallic and metallic substrates. Nationwide results are provided. The indoor floor dust lead (PbD) geometric mean (GM) was 8.8 microg/m2 (0.8 microg/ft2) and 6.8 mmicrog/m2 (0.6 mg/ft2) for total and leachable lead respectively; 0.21% of homes had an indoor PbD loading above 430.5 microg/m2 (40 microg/ft2). The outdoor play area concentration GM was 33.5microg/kg and 21.7microgkg in total and leachable lead respectively; 1.4% of concentrations were higher than or equal to 400microg/kg. Outdoor floor PbD GM was 44.4 mg/m2 (4.1 mg/ft2) that was approximately 3.2 times higher than the GM of indoor PbD. Lead-based paint (LBP) was present in 25% of dwellings, LBP on only non-metallic substrates was present in 19% of homes and on metallic substrates in 10% of dwellings. The GM of lead concentrations in tap water was below 1 microg/L; 58% of concentrations were lower than 1 microg/L and 2.9% were higher than or equal to 10 mg/L. The age cut-off for homes with lead would be 1974 for paint and 1993 for indoor floor dust. This study provides, for the first time, a look at the state of lead contamination to which children are exposed in French housing. Moreover, it provides policy makers an estimate of the number of French dwellings sheltering children where abatement should be conducted.
Environmental Research

hal-00714516
https://hal.archives-ouvertes.fr/hal-00714516

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
A set of four reactive flow-through experiments at temperature T = 100 degrees C and total pressure P=12 MPa was performed in limestone reservoir samples. By using various ranging from 0.7 to 10 MPa, these experiments mimic mass transfers occurring (1) near the injection well, where the brine is almost saturated with CO2 (i.e. P-CO2 approximate to P), and (2) at increasing distances from the injection well, where the fluid displays lower values and higher divalent cation concentrations due rock dissolution along the fluid pathway. Results for P-CO2 = 10 MPa show non-uniform dissolution features associated with transport-controlled mass transfer, while reaction-controlled uniform dissolution is observed for P-CO2 = 2.5 MPa. The experiment with P-CO2 = 6 MPa allows investigating in detail the transition from transport-to reaction-controlled dissolution. Conversely, the experiment reproducing conditions far from the injection well (P-CO2 = 0.7 MPa), shows a decrease of porosity triggered by the precipitation of Mg-rich calcite. For all the dissolution experiments, the time-resolved porosity phi(t) can be modeled by a simple non-linear equation including parameters that characterise the dissolution regime triggered by the reactivity of the inlet fluid (measured by the Damkohler number, Da). Furthermore, all dissolution experiments display power scaling between permeability (k) and porosity (phi) with distinctly different scaling exponents characterising the reactivity of the fluid percolating the sample, independently from the decrease with time of the reactive surface area. It is shown also that dissolution at moderate positive values of Da seems the most efficient to increase permeability and promote a rapid spreading of the reaction front, while inducing minimal modification of the porosity in the vicinity of the CO2 injection well. These results can be used to parameterize the k-phi function for modeling the earliest dissolution processes occurring in the vicinity of the reaction front.
ISSN: 0009-2541

hal-00445277
https://hal.archives-ouvertes.fr/hal-00445277
DOI : 10.1016/j.chemgeo.2009.03.028

Éditeur(s) : Amer Geophysical Union
Résumé : Benthic foraminiferal Mg/Ca has been shown to have great potential as a proxy for reconstructing deep water temperatures. However, the exact relationship between Mg uptake in benthic foraminifera and temperature is still ambiguous, and further exploration and refinement is much needed to reduce uncertainties associated with the method. Here, we present new core-top Mg/Ca data from benthic foraminiferal species from the lower part of the thermocline in the western tropical Atlantic (northern Brazilian margin). This area is unusual in that the changes in carbonate chemistry along the transect are very small, making it an ideal region for isolating and studying the role of temperature in the incorporation of Mg into the benthic shells. Our results show that benthic foraminiferal Mg/Ca largely reflects temperature in this area. Our data are combined with previously published data to produce new and improved Mg/Ca calibration equations for a number of benthic foraminiferal species within the Atlantic Ocean. Our study provides the first C. wuellerstorfi Mg/Ca data for the 46 degrees C temperature range and indicates that C. wuellerstorfi Mg/Ca is strongly controlled by temperature. As a result, the newly established C. wuellerstorfi calibration over the entire 06 degrees C temperature range is significantly improved with respect to previously published C. wuellerstorfi calibrations limited to the coldest part between 0 and 4 degrees C. Other benthic species (Cibicidoides kullenbergi, Globocassidulina subglobosa, Uvigerina peregrina, and Oridorsalis umbonatus) have also been studied, although these results are less conclusive.
Geochemistry Geophysics Geosystems (1525-2027) (Amer Geophysical Union), 2013-04 , Vol. 14 , N. 4 , P. 929-946

Droits : 2013. American Geophysical Union. All Rights Reserved.
http://archimer.ifremer.fr/doc/00181/29191/27596.pdf
DOI:10.1002/ggge.20043
http://archimer.ifremer.fr/doc/00181/29191/

Résumé : Dans cette thèse, nous présentons deux modèles mathèmatiques qui simulent la dynamique d'une épidémie de dengue à Cuba. Le premier modèle est décrit par un système d'équations différentielles ordinaires dans le but d'estimer certains paramètres essentiels dans l'évolution de l'èpidérnie. Le deuxième modèle utilise une inclusion différentielle afin de simuler la dynamique sous incertitudes. Nous passons aussi en revue une famille de modèles d'équations différentielles pour l'épidémie de VIH/SIDA à Cuba et nous reformulons l'un de ces modèles en une inclusion différentielle. En outre, pour analyser le comportement de ces deux épidémies et l'effet de l'intervention nous développons un algorithme pratique pour le calcul des ensembles atteignables des inclusions différentielles, qui fournit un cadre mathématique nous permettant de faire des prédictions appropriées de toutes les variables d'état des modèles
Ln this work we present two mathematical models that simulate the dynamics of an epidemic outbreak of dengue disease in Cuba. The i first model is described by a system of ordinary differential equations with the purpose of estimaling some essential parameters in the evolution of the epidemie. The second model uses a differential inclusion in order to simulate the dynamic under uncertainties. Also, we review a family of ordinary differential equations models of HIV/AIDS epidemic in Cuba and one of these models is reformulated as a differential inclusion. In addition, to analyze the behavior of these two epidemies and the effect of intervention, we develop a practical algorithm for the computation of the reachable sets of the differential inclusions, providing a mathematical framework allowing us to make suitable predictions of aII state variables of the models at a future time.

http://www.theses.fr/2011AGUY0413

Éditeur(s) : HAL CCSD European Geosciences Union
Résumé : We designed a thermo-mechanical numerical model for fast-spreading mid-ocean ridge with variable viscosity, hydrothermal cooling, latent heat release, sheeted dyke layer, and variable melt intrusion possibilities. The model allows for modulating several accretion possibilities such as the "gabbro glacier" (G), the "sheeted sills" (S) or the "mixed shallow and MTZ lenses" (M). These three crustal accretion modes have been explored assuming viscosity contrasts of 2 to 3 orders of magnitude between strong and weak phases and various hydrothermal cooling conditions depending on the cracking temperatures value. Mass conservation (stream-function), momentum (vorticity) and temperature equations are solved in 2-D cartesian geometry using 2-D, alternate direction, implicit and semi-implicit finite-difference scheme. In a first step, an Eulerian approach is used solving iteratively the motion and temperature equations until reaching steady states. With this procedure, the temperature patterns and motions that are obtained for the various crustal intrusion modes and hydrothermal cooling hypotheses display significant differences near the mid-ocean ridge axis. In a second step, a Lagrangian approach is used, recording the thermal histories and cooling rates of tracers travelling from the ridge axis to their final emplacements in the crust far from the mid-ocean ridge axis. The results show that the tracer's thermal histories are depending on the temperature patterns and the crustal accretion modes near the mid-ocean ridge axis. The instantaneous cooling rates obtained from these thermal histories betray these discrepancies and might therefore be used to characterize the crustal accretion mode at the ridge axis. These deciphering effects are even more pronounced if we consider the average cooling rates occurring over a prescribed temperature range. Two situations were tested at 1275-1125 °C and 1050-850 °C. The first temperature range covers mainly the crystallization range that is characteristic of the high temperature areas in the model (i.e. the near-mid-oceanic-ridge axis). The second temperature range corresponds to areas in the model where the motion is mainly laminar and the vertical temperature profiles are closer to conductive. Thus, this situation results in less discriminating efficiency among the crustal accretion modes since the thermal and dynamic properties that are described are common to all the crustal accretion modes far from the ridge axis. The results show that numerical modeling of thermo-mechanical properties of the lower crusts may bring useful information to characterize the ridge accretion structure, hydrothermal cooling and thermal state at the fast-spreading ridges and may open discussions with petrological cooling rate results.
ISSN: 1991-959X

hal-00907012
https://hal.archives-ouvertes.fr/hal-00907012
DOI : 10.5194/gmd-6-1659-2013

Éditeur(s) : Wiley-blackwell
Résumé : 1. Approximately 300 pelagic fish species naturally aggregate around floating objects (FOBs) at the surface of the oceans. Currently, more than 50% of the world catch of tropical tuna comes from the industrial tuna fisheries around drifting FOBs. Greater understanding of the complex decision-making processes leading to this aggregation pattern and the impact of the massive release of artificial FOBs by fishermen on the spatial distribution and management of tuna is needed. 2. We analyse how the interplay between social (relationships between individuals) and non-social (responses to the environment) behaviours may affect the spatial distribution of a population in a multi-FOB environment. Taking the example of tropical tunas associating with FOBs and using differential equations and stochastic simulations, we examine how, when increasing the number of FOBs, fish aggregation dynamics and the distribution of the population among patches are affected by the population size, level of sociality and the natural retentive and/or attractive forces of FOBs on individual tuna. 3. Our model predicts that, depending on the species' level of sociality, fish will be scattered among FOBs or aggregated around a single FOB based on the number of FOBs deployed in a homogeneous oceanic region. 4. For social species, we demonstrated that the total fish catch is reduced with increasing FOBs number. Indeed, for each size of population, there are a number of FOBs minimizing the total population of fish associated with FOBs and another number of FOBs maximizing the total population of associated fish. 5. Synthesis and applications. In terms of fisheries management, the total catch volume is directly linked to the total number of floating objects (FOBs) for non-social species, and any limit on the number of sets would then result in a limit on the total catch. For social species (e.g. tuna), however, increasing the number of FOBs does not necessarily lead to an increase in the total catch, which is a non-intuitive result. Indeed, our model shows that, for specific values of the parameters, deploying a greater number of FOBs in the water (all other parameters being constant) does not necessarily help fishermen to catch more tuna, but does increase the level of fishing effort and bycatch.
Journal Of Applied Ecology (0021-8901) (Wiley-blackwell), 2013-10 , Vol. 50 , N. 5 , P. 1081-1092

Droits : 2013 The Authors. Journal of Applied Ecology, 2013 British Ecological Society
http://archimer.ifremer.fr/doc/00151/26275/24439.pdf
DOI:10.1111/1365-2664.12140
http://archimer.ifremer.fr/doc/00151/26275/

Éditeur(s) : HAL CCSD
Résumé : poster presentation, 22nd European Meeting on Hypertension and Cardiovascular protection, London,26-29 April 2012
OBJECTIVE: Several studies demonstrate that the perception of overweight is associated with attempts at weight control in overweight subjects. Our objective is to describe the factors associated with the perception of overweight in an adult Caribbean population, and in particular, to assess the relationship between the perception of overweight and previous medical diagnosis of overweight. METHOD AND DESIGN: Consant was a cross-sectional study carried out in 2007 on a representative sample of the adult Guadeloupean population. Included were 1,005 subjects aged 25-74 years, drawn from stratified random sampling, and interviewed at home. The perception of overweight was evaluated by the question: "Do you consider yourself to be overweight?" with a binary response. RESULTS: Among overweight subjects (Body Mass Index ≥ 25 kg/m2, n = 576), 38.6% provided an incorrect assessment of their weight status. This proportion falls to 17.4% in those who stated to have previously received a medical diagnosis of overweight. However, only 48.8% of overweight subjects stated to have received such a diagnosis. A logistic regression shows that the underestimation of weight status is associated with the absence of previous diagnosis for overweight (OR: 5.35 - p < 10-3), as well as an age greater than or equal to 55 years (OR: 2.91 - p < 10-3), a BMI of less than 30 kg/m² (OR: 2.26 - p: 0.001), the male sex (OR: 1.86 - p: 0.004), and a low income level (OR: 1.62 - p: 0.030), but not a lack of awareness regarding the role of weight control in the prevention of cardiovascular diseases. Similar results are observed if waist circumference is taken as a factor instead of BMI. CONCLUSION: In this population, the lack of medical diagnosis of overweight was the leading factor associated with misperception of overweight. Screening for overweight therefore appears to be one of the preconditions to weight management, and remains a fundamental but often unused element in the fight against obesity.
https://hal.univ-antilles.fr/hal-00739785

Droits : info:eu-repo/semantics/OpenAccess
hal-00739785
https://hal.univ-antilles.fr/hal-00739785
https://hal.univ-antilles.fr/hal-00739785/document
https://hal.univ-antilles.fr/hal-00739785/file/The_lacksur screening_is_the_leading_factor_associated_with_the_misperceptionsur overweight_cor.pdf

Éditeur(s) : HAL CCSD Society for Industrial and Applied Mathematics
Résumé : International audience
In this paper, we developed a theoretical study for nonconservative sytems in one dimension in order to construct numerical schemes for solving the Riemann problem. The nonconservative form of our model system required the use of a well-adapted theory in order to give us a sense of our problem. We chose a framework of generalized functions for solving a scalar hyperbolic equation with a discontinuous coefficient $sigma_t +usigma_x approx 0$, where u is the velocity solution of a Burgers's equation. After an explicit solution of the Riemann problem, we derived Godunov split schemes for computing an approximate solution of the Cauchy problem. We applied our study to a system modeling elasticity and a system modeling gas dynamics. Some stability properties of a scheme and its convergence to a generalized solution are proved for the first model. Numerical experiments confirmed this convergence result. For the second model, calculations of flows containing weak-to-moderate shocks showed that conservation errors are reduced when the mesh is refined but were not entirely eliminated.
ISSN: 0036-1429

hal-00770266
https://hal.univ-antilles.fr/hal-00770266
DOI : 10.1137/S0036142900378637